I2C PROTOCOL Of ARM ( LPC2148 )

• What is I2C ? – I²C (Inter-Integrated Circuit)(alternately spelled I2C or IIC)(most commonly pronounced I-squared-C) is a multimaster serial single-ended computer bus invented by the Philips semiconductor division, today NXP Semiconductors, and used for attaching low-speed peripherals to main system.

• How I2C protocol work – The I2C protocol requires only 2 signals: clock and data.  Clock is known as SCL or SCK (for Serial Clock), while data is known as SDA (for Serial Data).  What makes I2C unique is the use of special combinations of signal conditions and changes.  Fundamentally, there are just two: Start and Stop.  A ‘START” condition is generated by the Master, followed by 7 bits of address, then a ReadWrite bit.  If a slave device detects an address match, it will send an ACK by driving SDA low during the next clock cycle; if no slave recognizes the address then the SDA line will be left alone to be pulled up high.  Following a successful ACK, data will be either sent to the slave device or read from the slave device (depending on what was indicated by the Read/Write bit).  Therefore, each byte is 9 bits: either 7 address plus one R/W plus one ACK/NAK, or 8 data plus one ACK/NAK.  The last data byte of a transaction should generally be followed by a NAK, to indicate that it is intended to be the final byte.  After this, either a STOP or a ReSTART should be issued by the Master. Bus errors are rarely introduced when using a dedicated I2C peripheral on the Master.

•   Feature of  I2C protocol

•  I2C protocol supports multiple data speeds: standard (100 kbps), fast (400 kbps) and high speed (3.4 Mbps) communications.
• Built in collision detection
• 10-bit Addressing
• Supports both Multi-master and Multi-master with Slave functions.
• Data broadcast (general call).
• Since only two wires are required, I2C is well suited for boards with many devices connected on the bus. This helps reduce the cost and complexity of the circuit as additional devices are added to the system.

• Applications-       The I2C bus is a great option for applications that require low cost and simple implementation rather than high speed. For example, reading certain memory ICs, accessing DACs and ADCs,reading sensors,access LCDs, transmitting and controlling user directed actions, reading hardware sensors, and communicating with multiple microcontrollers are common uses of the I2C communication protocol.I2C also used for attaching low-speed peripherals to a motherboard, embedded system, cellphone, or other digital electronic devices. Several competitors, such as Siemens AG (later Infineon Technologies AG, now Intel mobile communications), NEC, Texas Instruments, STMicroelectronics (formerly SGS-Thomson), Motorola (later Freescale), and Intersil, have introduced compatible I²C products to the market since the mid-1990s.

 Click Here : Depth understanding of I2C Protocol

coming   soon……

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 1.  Program write and read data from EEPROM 24LC04 by I2C Protocol  with arm (lpc2148) and send data to through UART 0.

/******************************************************
www.firmcodes.com
DEVELOPED BY:- FIRMWARE DEVELOPER
WHAT PROGRAM DO:-This Program write and read data from EEPROM 24LC04 by I2C Protocol 
with arm ( lpc2148 ) and send data to through UART.
******************************************************/



#include  <lpc214x.h>		   //Includes LPC2148 register definitions

#define MAX_BUFFER_SIZE 16
#define DEVICE_ADDR 0xA0
#define BLK_0 0x00
#define BLK_1 0x02
#define MAX_BLOCK_SIZE 256

#define LED1_ON() IO1SET=(1<<16)		//I2C write indicator
#define LED2_ON() IO1SET=(1<<17)		//I2C read indicator
#define LED3_ON() IO1SET=(1<<18)		//Comm failure indicator
#define LED4_ON() IO1SET=(1<<19)		//Comm success indicator

#define LED1_OFF() IO1CLR=(1<<16)	
#define LED2_OFF() IO1CLR=(1<<17)
#define LED3_OFF() IO1CLR=(1<<18)
#define LED4_OFF() IO1CLR=(1<<19)

#define Fosc            12000000                    
#define Fcclk           (Fosc * 5)                  
#define Fcco            (Fcclk * 4)                 
#define Fpclk           (Fcclk / 4) * 1            

#define  UART_BPS	9600	 //Set Baud Rate here



void Delay(unsigned char j);
void Init_UART0(void);
void UART0_SendByte(unsigned char data);
void UART0_SendStr(const unsigned char *str);
void Send_Start(void);
void Send_Stop(void);
unsigned char Send_I2C(unsigned char *Data,unsigned char Len);
unsigned char Read_I2C(unsigned char *Data,unsigned char Len);
unsigned char Page_Write(unsigned char BLOCK_NUMBER,unsigned char BLOCK_ADDR);
unsigned char Page_Read(unsigned int BLOCK_NUMBER,unsigned char BLOCK_ADDR);
unsigned char I2C_Status(unsigned char status_code);


unsigned char I2C_WR_Buf[MAX_BUFFER_SIZE]={"  FIRMCODES  "};
unsigned char I2C_RD_Buf[MAX_BUFFER_SIZE];
unsigned char Status=0;
unsigned char Status_Flag=0;

void  Delay(unsigned char j)
{  
 unsigned int  i;
 for(;j>0;j--)
 {
  for(i=0; i<60000; i++);
 } 
}



void  Init_UART0(void)
{  
   unsigned int Baud16;
   U0LCR = 0x83;		            // DLAB = 1
   Baud16 = (Fpclk / 16) / UART_BPS;  
   U0DLM = Baud16 / 256;							
   U0DLL = Baud16 % 256;						
   U0LCR = 0x03;
}
				

void UART0_SendByte(unsigned char data)
{  
   U0THR = data;				    
   while( (U0LSR&0x40)==0 );
   return;	    
}
                               

void  UART0_SendStr(const unsigned char *str)	 //A function to send a string on UART0
{  
   while(1)
   {  
      if( *str == '\0' ) break;
      UART0_SendByte(*str++);	    
   }
}


void Send_Start()
{
 I2C0CONSET=0x20; 
}


void Send_Stop()
{
 I2C0CONSET=0x10;
}



// This function sends sequential data to the EEPROM 24LC04
// The buffer size for EEPROM 24LC04 is 16 bytes
// The Len parameter should not exceed this value
unsigned char Send_I2C(unsigned char *Data,unsigned char Len)
{
 while(Len)
 {
  I2C0DAT=*Data;
  if(I2C_Status(0x28))
  {
   return 1;
  }
  Len--;
  Data++;
 }
 return 0;
}


// This function reads random data from the EEPROM 24LC04

unsigned char Read_I2C(unsigned char *Data,unsigned char Len)
{
 while(Len)
 {
  if(Len==1)  //Last byte
  {
   I2C0CONCLR=0x04;		 //set hardware to send nack
   if(I2C_Status(0x58))	//last byte has been received and NACK has been returned
   {
    return 1;
   }
   *Data=I2C0DAT;
  }
  else
  {
   I2C0CONSET=0x04;	 		//set hardware to send  ack
   if(I2C_Status(0x50))	//Byte has been received ACK has been returned
   {
    return 1;
   }
   *Data=I2C0DAT;	
  } 
  Data++;
  Len--;
 }
 return 0;
}


unsigned char I2C_Status(unsigned char status_code)
{
 while(Status_Flag==0);
 Status_Flag=0;
 if(Status!=status_code)
 {
  return 1;
 }
 else
 {
  return 0;
 }
}


unsigned char Page_Write(unsigned char BLOCK_NUMBER,unsigned char BLOCK_ADDR)
{
 Send_Start();
 if(I2C_Status(0x08))	//Start has been transmitted
 {
  return 1;
 }

 I2C0DAT=DEVICE_ADDR | BLOCK_NUMBER;	// Send Address
 if(I2C_Status(0x18))					//Device address, block num and write has been transmitted
 {
  return 1;
 }

 I2C0DAT=BLOCK_ADDR;	// Send block address
 if(I2C_Status(0x28))	//Block address has been transmitted
 {
  return 1;
 }

 if(Send_I2C(I2C_WR_Buf,MAX_BUFFER_SIZE))			//Send Data
 {
  Send_Stop();
  return 1;
 }
 Send_Stop();
 return 0;
}


unsigned char Page_Read(unsigned int BLOCK_NUMBER,unsigned char BLOCK_ADDR)
{
 Send_Start();
 if(I2C_Status(0x08))	//Start has been transmitted
 {
  return 1;
 }

 I2C0DAT=DEVICE_ADDR | BLOCK_NUMBER;	// Send Address
 if(I2C_Status(0x18))	//Device address, block num and write has been transmitted
 {
  return 1;
 }

 I2C0DAT=BLOCK_ADDR;
 if(I2C_Status(0x28))	//Block address has been transmitted
 {
  return 1;
 }

 Send_Start();		     // Repeat Start
 if(I2C_Status(0x10))	//Repeated Start has been transmitted
 {
  return 1;
 }

 I2C0DAT=DEVICE_ADDR | BLOCK_NUMBER | 0x01;			//Device address, block num and read has been transmitted
 if(I2C_Status(0x40))	//
 {
  return 1;
 }
 if(Read_I2C(I2C_RD_Buf,MAX_BUFFER_SIZE))			//Receive 16bytes of Data from EEPROM
 {
  Send_Stop();
  return 1;
 }
 Send_Stop();
 return 0;
}


void  __irq I2C0_Status(void)
{ 
  Status_Flag=0xFF; 			//update status flag
  Status=I2C0STAT;				//Read Status byte
  I2C0CONCLR=0x28;				
  VICVectAddr = 0x00;   		//Acknowledge Interrupt
}	


void I2C_Init()
{
 PINSEL0&=0xFFFFFF0F;
 PINSEL0|=0x00000050;

 I2C0CONCLR=0x6C;
 I2C0CONSET=0x40;
 I2C0SCLH=80;
 I2C0SCLL=70;

 /*  Init VIC for I2C0	*/
 VICIntSelect = 0x00000000;		// Setting all interrupts as IRQ(Vectored)
 VICVectCntl0 = 0x20 | 9;		// Assigning Highest Priority Slot to I2C0 and enabling this slot
 VICVectAddr0 = (unsigned long)I2C0_Status; // Storing vector address of I2C0
 VICIntEnable = (1<<9);	

}

int  main(void)
{  
 PINSEL0 = 0x00000005;		// Enable GPIO on all pins
 PINSEL1 = 0x00000000;
 PINSEL2 = 0x00000000;
 IO1DIR = (1<<19) | (1<<18) | (1<<17) | (1<<16);		// Set P1.16, P1.17, P1.18, P1.19 as Output
 LED1_OFF();LED2_OFF();LED3_OFF();LED4_OFF();
 Init_UART0();
 I2C_Init();
 
 LED1_ON();  //Write Indicator
 if(Page_Write(BLK_1,0x00))
 {
  UART0_SendStr("Write Failed");
  LED3_ON();
 }
 LED1_OFF();

 Delay(1);

 LED2_ON();	//Read indicator
 if(Page_Read(BLK_1,0x00))
 {
  UART0_SendStr("Read Failed");
  LED3_ON();
 }
 else
 {
  UART0_SendStr(I2C_RD_Buf);
  LED4_ON();
 }
 LED2_OFF();
 while(1)
 {
  
 }	
 
 
}

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